1. Field of the Invention
The invention relates to the disposition of generator circuit-breakers in an electric power station.
2. Description of the Prior Art
The increase in the power of power stations increases the short-circuit current cut-out performances required of generator circuit-breakers.
Moreover, when the power of the generator is high, a configuration is often adopted in which a generator feeds two sets of bars connected to two separate circuits: two networks or two portions of networks, through two transformers each connected to the generator by a circuit-breaker. In the case of a short-circuit, for example between one of the transformers and the corresponding circuit-breaker, the said circuit-breaker must cut out a short-circuit current which is the sum of the current discharged by the generator and the current discharged by the other transformer. The extension of this already produced configuration could be provided for feeding more than two transformers with a single generator.
These dispositions are particularly advantageous when the powers of the generators are very high. Firstly, they increase the reliability of the network, for it is possible to discharge a part of the power, in the case of a breakdown, on the line which is not affected or the lines which are affected by the failure. Secondly, these dispositions facilitate the production of the transformers since the manufacturing and transport of very large units is difficult.
Furthermore, this configuration leads to the increasing of the short-circuit current which the circuit-breakers of the generators must cut, since the short-circuit current coming from the network or networks not affected by the failure is added to the generator short-circuit current. Now, in a high-power circuit-breakers it is generally much more difficult to increase the cut-out power than the closing power or the short-circuit current withstood during a short space time.